Objective—To determine concentrations of marbofloxacin
in alveolar macrophages (AMs) and epithelial
lining fluid (ELF) and compare those concentrations
with plasma concentrations in healthy dogs.
Animals—12 adult mixed-breed and purebred
Procedure—10 dogs received orally administered marbofloxacin
at a dosage of 2.75 mg/kg every 24 hours for
5 days. Two dogs served as nontreated controls.
Fiberoptic bronchoscopy and bronchoalveolar lavage
procedures were performed while dogs were anesthetized
with propofol, approximately 6 hours after the
fifth dose. The concentrations of marbofloxacin in plasma
and bronchoalveolar fluid (cell and supernatant fractions)
were determined by use of high-performance liquid
chromatography with detection of fluorescence.
Results—Mean ± SD plasma marbofloxacin concentrations
2 and 6 hours after the fifth dose were 2.36 ±
0.52 µg/mL and 1.81 ± 0.21 µg/mL, respectively.
Mean ± SD marbofloxacin concentration 6 hours after
the fifth dose in AMs (37.43 ± 24.61 µg/mL) was significantly
greater than that in plasma (1.81 ± 0.21
µg/mL) and ELF (0.82 ± 0.34 µg/mL), resulting in a
mean AM concentration-to-plasma concentration
ratio of 20.4, a mean AM:ELF ratio of 60.8, and a
mean ELF-to-plasma ratio of 0.46. Marbofloxacin was
not detected in any samples from control dogs.
Conclusions and Clinical Relevance—Marbofloxacin
concentrations in AMs were greater than the mean
inhibitory concentrations of major bacterial pathogens
in dogs. Results indicated that marbofloxacin accumulates
in AMs at concentrations exceeding those
reached in plasma and ELF. The accumulation of marbofloxacin
in AMs may facilitate treatment for susceptible
intracellular pathogens or infections associated
with pulmonary macrophage infiltration. (Am J Vet Res